Buggy code:
public void testGetFile_Parent ( ) { } public void testGetTempDirectoryPath ( ) { } public void testGetTempDirectory ( ) { } public void testGetUserDirectoryPath ( ) { } public void testGetUserDirectory ( ) { } public void test_openInputStream_exists ( ) throws Exception { } public void test_openInputStream_existsButIsDirectory ( ) throws Exception { } public void test_openInputStream_notExists ( ) throws Exception { } void openOutputStream_noParent ( boolean createFile ) throws Exception { } public void test_openOutputStream_noParentCreateFile ( ) throws Exception { } public void test_openOutputStream_noParentNoFile ( ) throws Exception { } public void test_openOutputStream_exists ( ) throws Exception { } public void test_openOutputStream_existsButIsDirectory ( ) throws Exception { } public void test_openOutputStream_notExists ( ) throws Exception { } public void test_openOutputStream_notExistsCannotCreate ( ) throws Exception { } public void testByteCountToDisplaySize ( ) { } public void testToFile1 ( ) throws Exception { } public void testToFile2 ( ) throws Exception { } public void testToFile3 ( ) throws Exception { } public void testToFile4 ( ) throws Exception { } public void testToFile5 ( ) throws Exception { } public void testToFileUtf8 ( ) throws Exception { } public void testDecodeUrl ( ) { } public void testDecodeUrlLenient ( ) { } public void testDecodeUrlNullSafe ( ) { } public void testDecodeUrlEncodingUtf8 ( ) { } public void testToFiles1 ( ) throws Exception { } public void testToFiles2 ( ) throws Exception { } public void testToFiles3 ( ) throws Exception { } public void testToFiles4 ( ) throws Exception { } public void testToURLs1 ( ) throws Exception { } public void testContentEquals ( ) throws Exception { } public void testContentEqualsIgnoreEOL ( ) throws Exception { } public void testCopyURLToFile ( ) throws Exception { } public void testCopyURLToFileWithTimeout ( ) throws Exception { } public void testForceMkdir ( ) throws Exception { } public void testSizeOfDirectory ( ) throws Exception { } public void testSizeOf ( ) throws Exception { } public void testIsFileNewerOlder ( ) throws Exception { } public void testCopyFile1 ( ) throws Exception { } public void testCopyFileToOutputStream ( ) throws Exception { } public void IGNOREtestCopyFileLarge ( ) throws Exception { } public void testCopyFile2 ( ) throws Exception { } public void testCopyToSelf ( ) throws Exception { } public void testCopyFile2WithoutFileDatePreservation ( ) throws Exception { } public void testCopyDirectoryToDirectory_NonExistingDest ( ) throws Exception { } public void testCopyDirectoryToNonExistingDest ( ) throws Exception { } public void testCopyDirectoryToExistingDest ( ) throws Exception { } public void testCopyDirectoryFiltered ( ) throws Exception { } public void testCopyDirectoryPreserveDates ( ) throws Exception { } public void testCopyDirectoryToChild ( ) throws Exception { } public void testCopyDirectoryToGrandChild ( ) throws Exception { } public void testCopyDirectoryToItself ( ) throws Exception { } private void createFilesForTestCopyDirectory ( File grandParentDir , File parentDir , File childDir ) throws Exception { } public void testCopyDirectoryErrors ( ) throws Exception { } public void testForceDeleteAFile1 ( ) throws Exception { } public void testForceDeleteAFile2 ( ) throws Exception { } public void testForceDeleteAFile3 ( ) throws Exception { } public void testCopyFile1ToDir ( ) throws Exception { } public void testCopyFile2ToDir ( ) throws Exception { } public void testForceDeleteDir ( ) throws Exception { } public void testFileUtils ( ) throws Exception { } public void testTouch ( ) throws IOException { } public void testListFiles ( ) throws Exception { } public void testListFilesWithDirs ( ) throws IOException { } public void testIterateFiles ( ) throws Exception { } public void testIterateFilesAndDirs ( ) throws IOException { } public void testReadFileToStringWithDefaultEncoding ( ) throws Exception { } public void testReadFileToStringWithEncoding ( ) throws Exception { } public void testReadFileToByteArray ( ) throws Exception { } public void testReadLines ( ) throws Exception { } public void testWriteStringToFile1 ( ) throws Exception { } public void testWriteStringToFile2 ( ) throws Exception { File file = new File ( getTestDirectory ( ) , "write.txt" ) ; <START_BUG> FileUtils . writeStringToFile ( file , "Hello<seq2seq4repair_space>//u1234" , null ) ; <END_BUG> byte [ ] text = "Hello<seq2seq4repair_space>//u1234" . getBytes ( ) ; assertEqualContent ( text , file ) ; } public void testWriteCharSequence1 ( ) throws Exception { } public void testWriteCharSequence2 ( ) throws Exception { } public void testWriteByteArrayToFile ( ) throws Exception { } public void testWriteLines_4arg ( ) throws Exception { } public void testWriteLines_4arg_Writer_nullData ( ) throws Exception { } public void testWriteLines_4arg_nullSeparator ( ) throws Exception { } public void testWriteLines_3arg_nullSeparator ( ) throws Exception { } public void testWriteLines_5argsWithAppendOptionTrue_ShouldNotDeletePreviousFileLines ( ) throws Exception { } public void testWriteLines_5argsWithAppendOptionFalse_ShouldDeletePreviousFileLines ( ) throws Exception { } public void testWriteLines_4argsWithAppendOptionTrue_ShouldNotDeletePreviousFileLines ( ) throws Exception { } public void testWriteLines_4argsWithAppendOptionFalse_ShouldDeletePreviousFileLines ( ) throws Exception { } public void testWriteLinesEncoding_WithAppendOptionTrue_ShouldNotDeletePreviousFileLines ( ) throws Exception { } public void testWriteLinesEncoding_WithAppendOptionFalse_ShouldDeletePreviousFileLines ( ) throws Exception { } public void testWriteLines_3argsWithAppendOptionTrue_ShouldNotDeletePreviousFileLines ( ) throws Exception { } public void testWriteLines_3argsWithAppendOptionFalse_ShouldDeletePreviousFileLines ( ) throws Exception { } public void testWriteStringToFileWithEncoding_WithAppendOptionTrue_ShouldNotDeletePreviousFileLines ( ) throws Exception { } public void testWriteStringToFileWithEncoding_WithAppendOptionFalse_ShouldDeletePreviousFileLines ( ) throws Exception { } public void testWriteStringToFile_WithAppendOptionTrue_ShouldNotDeletePreviousFileLines ( ) throws Exception { } public void testWriteStringToFile_WithAppendOptionFalse_ShouldDeletePreviousFileLines ( ) throws Exception { } public void testWriteWithEncoding_WithAppendOptionTrue_ShouldNotDeletePreviousFileLines ( ) throws Exception { } public void testWriteWithEncoding_WithAppendOptionFalse_ShouldDeletePreviousFileLines ( ) throws Exception { } public void testWrite_WithAppendOptionTrue_ShouldNotDeletePreviousFileLines ( ) throws Exception { } public void testWrite_WithAppendOptionFalse_ShouldDeletePreviousFileLines ( ) throws Exception { } public void testWriteByteArrayToFile_WithAppendOptionTrue_ShouldNotDeletePreviousFileLines ( ) throws Exception { } public void testWriteByteArrayToFile_WithAppendOptionFalse_ShouldDeletePreviousFileLines ( ) throws Exception { } public void testChecksumCRC32 ( ) throws Exception { } public void testChecksum ( ) throws Exception { } public void testChecksumOnNullFile ( ) throws Exception { } public void testChecksumOnNullChecksum ( ) throws Exception { } public void testChecksumOnDirectory ( ) throws Exception { } public void testChecksumDouble ( ) throws Exception { } public void testDeleteQuietlyForNull ( ) { } public void testDeleteQuietlyDir ( ) throws IOException { } public void testDeleteQuietlyFile ( ) throws IOException { }

Fix:
FileUtils . writeStringToFile ( file , "Hello<seq2seq4repair_space>//u1234" , ( ( String ) ( null ) ) ) ;